use-ide-background-window

Arguments:
configuration

Returns (or sets with setf) whether the optional IDE background window
is displayed. This window is useful mostly for covering other
applications that may be distracting when they are visible between the
IDE's multiple top-level windows. This option has an effect only when
the use-ide-parent-window option is
nil, because otherwise there is only a single
top-level window through which other applications do not show.

The background window also has a right-button shortcut menu that lists
all current IDE windows that aren't shrunk (hidden). Selecting a
window on this menu brings the window to the front and gives it the
keyboard focus.

Changing this property while the IDE is running will toggle the
background window off or on. When the IDE is started up, the
background window will appear if it was there whenever the
configuration options were most recently saved.